1. Field of the Invention
The present invention relates to a control device of an internal combustion engine.
2. Description of the Related Art
Known in the art is a control device of an internal combustion engine setting an intake air amount (that is, target intake air amount) in accordance with an amount of depression of an accelerator expressing a demand of the driver of the vehicle, etc., finding a target opening degree of the throttle valve based on the target intake air amount (that is, target throttle opening degree), and controlling the throttle valve to this target throttle opening valve to control the intake air amount (for example, see Japanese Unexamined Patent Publication No. 5-65845).
In such a control device of an internal combustion engine, it is preferable to judge if a control abnormality occurs in setting the target throttle opening degree based on the target intake air amount and the control of the opening degree of the throttle valve following that. As the method for judging the existence of any such control abnormality, the method may be considered of comparing the requested throttle opening degree able to be determined from the accelerator depression and engine speed and the actual throttle opening degree measured by a throttle opening degree sensor, but in actuality, these two throttle opening degrees sometimes do not match. Therefore, with this method, it is sometimes not possible to accurately judge the existence of a control abnormality.
That is, for example, when an electronic control type transmission is mounted or when a system is mounted for preventing sideways sliding etc. and stabilizing the vehicle by controlling the engine output, since the target intake air amount is determined based on the acceleration depression and engine speed expressing the demand of the driver and also the operating state of the vehicle or engine, the requested throttle opening degree and the target throttle opening degree do not necessarily match and, as a result, even if the control is normal, the requested throttle opening degree and actual throttle opening degree sometimes do not match. Further, in a system controlling the throttle opening degree and the opening characteristics of the intake valve (for example, the lift etc.) so as to control the intake air amount, the throttle opening degree realizing the same target intake air amount will differ depending on the opening characteristics of the intake valve, so sometimes the requested throttle opening degree and the target throttle opening degree will not match and therefore sometimes the requested throttle opening degree and actual throttle opening degree will not match.